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The problem of deciding whether a set of quantum measurements is jointly measurable is known to be equivalent to determining whether a quantum assemblage is unsteerable. This problem can be formulated as a semidefinite program (SDP).…

Quantum systems, in general, output data that cannot be simulated efficiently by a classical computer, and hence is useful for solving certain mathematical problems and simulating quantum many-body systems. This also implies, unfortunately,…

Quantum Physics · Physics 2017-10-04 Keisuke Fujii , Masahito Hayashi

Quantum computers are on the brink of surpassing the capabilities of even the most powerful classical computers. This naturally raises the question of how one can trust the results of a quantum computer when they cannot be compared to…

We propose quantum circuits to test interferometric complementarity using symmetric two-way interferometers coupled to a which-path detector. First, we consider the two-qubit setup in which the controlled transfer of path information to the…

Quantum Physics · Physics 2021-09-29 Pedro M. Q. Cruz , J. Fernández-Rossier

We formulate and study, in general terms, the problem of quantum system identification, i.e., the determination (or estimation) of unknown quantum channels through their action on suitably chosen input density operators. We also present a…

Quantum Physics · Physics 2007-05-23 Maxim Raginsky

We analyze the complexity of quantum state verification in the context of solving systems of linear equations of the form $A \vec x = \vec b$. We show that any quantum operation that verifies whether a given quantum state is within a…

Quantum Physics · Physics 2021-02-24 Rolando D. Somma , Yigit Subasi

Basing on states and channels isomorphism we point out that semidefinite programming can be used as a quick test for nonzero one-way quantum channel capacity. This can be achieved by search of symmetric extensions of states isomorphic to a…

Quantum Physics · Physics 2015-06-26 Pawel Horodecki , Marcin L. Nowakowski

By preparing an input state and measuring an observable for the output state, we can measure a quantum channel. Following the formulation given by Xiao et al., we study an uncertainty relation for ancilla-free measurements of random unitary…

Quantum Physics · Physics 2023-03-22 Taihei Kimoto , Takayuki Miyadera

A quantum channel is said to be a mixed-unitary channel if it can be expressed as a convex combination of unitary channels. We prove that, given the Choi representation of a quantum channel, it is NP-hard with respect to polynomial-time…

Quantum Physics · Physics 2020-04-22 Colin Do-Yan Lee , John Watrous

An important distinction in our understanding of capacities of classical versus quantum channels is marked by the following question: is there an algorithm which can compute (or even efficiently compute) the capacity? While there is…

Quantum Physics · Physics 2026-03-31 Archishna Bhattacharyya , Arthur Mehta , Yuming Zhao

Quantum computers promise to efficiently solve not only problems believed to be intractable for classical computers, but also problems for which verifying the solution is also considered intractable. This raises the question of how one can…

Quantum Physics · Physics 2018-07-10 Alexandru Gheorghiu , Theodoros Kapourniotis , Elham Kashefi

Quantum mechanics predicts that measurements of incompatible observables carry a minimum uncertainty which is independent of technical deficiencies of the measurement apparatus or incomplete knowledge of the state of the system. Nothing yet…

Quantum Physics · Physics 2013-06-14 Davide Girolami , Tommaso Tufarelli , Gerardo Adesso

We present a quantum circuit that implements a non-demolition measurement of complementary single- and bi-partite properties of a two-qubit system: entanglement and single-partite visibility and predictability. The system must be in a pure…

Quantum Physics · Physics 2007-06-20 F. de Melo , S. P. Walborn , János A. Bergou , L. Davidovich

Quantum computing promises exponential speed-ups for important simulation and optimization problems. It also poses new CAD problems that are similar to, but more challenging, than the related problems in classical (non-quantum) CAD, such as…

Quantum Physics · Physics 2011-11-04 George F. Viamontes , Igor L. Markov , John P. Hayes

We study two kinds of different problems. One is the multiple independence testing, which can be considered as a kind of generalization of quantum Stein's lemma. We test whether the quantum system is correlated to the classical system or is…

Quantum Physics · Physics 2025-08-05 Ayanava Dasgupta , Naqueeb Ahmad Warsi , Masahito Hayashi

We provide a feasible necessary and sufficient condition for when an unknown quantum operation (quantum device) secretely selected from a set of known quantum operations can be identified perfectly within a finite number of queries, and…

Quantum Physics · Physics 2013-05-29 Runyao Duan , Yuan Feng , Mingsheng Ying

In this paper we give an overview of the quantum computational complexity class QMA and a description of known QMA-complete problems to date. Such problems are believed to be difficult to solve, even with a quantum computer, but have the…

Quantum Physics · Physics 2014-04-29 Adam D. Bookatz

This paper presents stronger methods of achieving perfect completeness in quantum interactive proofs. First, it is proved that any problem in QMA has a two-message quantum interactive proof system of perfect completeness with constant…

Quantum Physics · Physics 2016-05-25 Hirotada Kobayashi , François Le Gall , Harumichi Nishimura

Quantum channel, as the information transmitter, is an indispensable tool in quantum information theory. In this paper, we study a class of special quantum channels named the mixed-permutation channels. The properties of these channels are…

Quantum Physics · Physics 2024-01-15 Lin Zhang , Ming-Jing Zhao

We review in a unified way a recently proposed method to detect properties of unknown quantum channels and lower bounds to quantum capacities, without resorting to full quantum process tomography. The method is based on the preparation of a…

Quantum Physics · Physics 2017-12-19 Chiara Macchiavello , Massimiliano F. Sacchi